Internal combustion gasoline engines run on a mixture of gasoline and air. Air enters the engine through an air intake chamber, otherwise referred to as an air cleaner or airbox, and proceeds through a series of tubes to the throttle body. The air is then distributed through a series of passages called the intake manifold, where it is circulated to the cylinders. An engine requires air mixed with gasoline (a typical mixture being approximately 14.7 parts of air to one part of gasoline). Accordingly, an engine's horsepower can be limited by the difficulty of getting enough air to the cylinders. It is, therefore, advantageous to limit any air flow restrictions when designing a vehicle's air induction system.
The air cleaner itself is significant not only for air intake, but also as a resonator (e.g., a Helmholtz resonator). A resonance effect occurs when an enclosed volume of a suitable size and shape is connected to the engine's intake manifold, causing the air inside to resonate at a frequency that results in pressure peaks coincident with the cylinders' intake stroke frequency. The system acoustically cancels sound pressure waves to achieve and maintain resonance characteristics. To achieve and maintain these resonance characteristics, it can be advantageous to design an air cleaner of a suitable acoustic volume.
The air cleaner, however, is typically among the last components designed into a vehicle's engine compartment. In order to utilize the minimal remaining space, engineers are typically required to design an air cleaner for each particular vehicle and engine combination. Accordingly, air cleaners are typically engine-mounted or body-mounted where space permits, which generally necessitates a complex piping scheme to route filtered air from the air cleaner into the engine. Turbocharged engines can further complicate air intake placement and piping due to the additional piping required to route filtered air from the air cleaner into the turbochargers and compressed air from the turbochargers to the engine via a charge air cooler. Similar concerns exist for supercharged engines. Such time, space, and design limitations can result in significant setbacks in air flow restriction and air cleaner acoustic volume, as well as additional trade-offs in air charge temperature and air cleaner serviceability.